127 lines
5.0 KiB
Python
127 lines
5.0 KiB
Python
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"""
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LangGraph 状态图构建模块 - 完全面向对象风格，无嵌套函数
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"""
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import operator
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import asyncio
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from typing import Literal, Annotated, Any
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from langchain_core.language_models import BaseLLM
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from langchain_core.messages import AnyMessage, AIMessage, ToolMessage, SystemMessage
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from langchain_core.prompts import ChatPromptTemplate, MessagesPlaceholder
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from langgraph.graph import StateGraph, START, END
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from typing_extensions import TypedDict
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class MessageState(TypedDict):
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"""对话状态类型定义"""
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messages: Annotated[list[AnyMessage], operator.add]
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llm_calls: int
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class GraphBuilder:
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"""LangGraph 状态图构建器 - 所有节点均为类方法"""
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def __init__(self, llm: BaseLLM, tools: list, tools_by_name: dict[str, Any]):
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"""
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初始化构建器
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Args:
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llm: 大语言模型实例
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tools: 工具列表
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tools_by_name: 名称到工具函数的映射
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"""
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self.llm = llm
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self.tools = tools
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self.tools_by_name = tools_by_name
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self._llm_with_tools = llm.bind_tools(tools)
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self._prompt = self._create_prompt()
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self._chain = self._prompt | self._llm_with_tools
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@staticmethod
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def _create_prompt() -> ChatPromptTemplate:
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"""创建系统提示模板（静态方法，无需访问实例）"""
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return ChatPromptTemplate.from_messages([
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SystemMessage(content=(
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"你是一个个人生活助手和数据分析助手。请说中文。"
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"当用户询问天气或温度时,使用get_current_temperature工具获取信息。"
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"当用户要求读文本文件时,请使用 read_local_file 工具,只能读取 './user_docs' 目录下的文件。"
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"当用户要求读PDF文件时,请使用 read_pdf_summary 工具,只能读取 './user_docs' 目录下的文件。"
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"当用户要求读Excel文件时,请使用 read_excel_as_markdown 工具,只能读取 './user_docs' 目录下的文件。"
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"当用户要求抓取网页时,请使用 fetch_webpage_content 工具。"
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"重要:你的回答必须简洁、直接,不要包含任何关于思考过程的描述。"
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)),
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MessagesPlaceholder(variable_name="message")
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])
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async def call_llm(self, state: MessageState) -> dict:
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"""
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LLM 调用节点（异步方法）
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注意：因为 self._chain.invoke 是同步方法，使用 run_in_executor 避免阻塞事件循环
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"""
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loop = asyncio.get_event_loop()
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response = await loop.run_in_executor(
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None,
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lambda: self._chain.invoke({"message": state["messages"]})
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)
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return {
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"messages": [response],
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"llm_calls": state.get('llm_calls', 0) + 1
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}
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async def call_tools(self, state: MessageState) -> dict:
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"""
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工具执行节点（异步方法）
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对于每个工具调用，在线程池中执行同步工具函数
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"""
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last_message = state['messages'][-1]
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if not isinstance(last_message, AIMessage) or not last_message.tool_calls:
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return {"messages": []}
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results = []
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loop = asyncio.get_event_loop()
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for tool_call in last_message.tool_calls:
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tool_name = tool_call["name"]
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tool_args = tool_call["args"]
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tool_id = tool_call["id"]
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tool_func = self.tools_by_name.get(tool_name)
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if tool_func is None:
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results.append(ToolMessage(content=f"Tool {tool_name} not found", tool_call_id=tool_id))
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continue
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try:
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# 同步工具函数在线程池中执行
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observation = await loop.run_in_executor(
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None,
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lambda: tool_func.invoke(tool_args)
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)
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results.append(ToolMessage(content=str(observation), tool_call_id=tool_id))
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except Exception as e:
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results.append(ToolMessage(content=f"Error: {e}", tool_call_id=tool_id))
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return {"messages": results}
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@staticmethod
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def should_continue(state: MessageState) -> Literal['tool_node', END]:
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"""
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条件边判断（静态方法）
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决定下一步是进入工具节点还是结束
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"""
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last_message = state["messages"][-1]
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if isinstance(last_message, AIMessage) and bool(last_message.tool_calls):
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return 'tool_node'
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return END
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def build(self) -> StateGraph:
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"""
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构建未编译的状态图（返回 StateGraph 实例）
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图中节点直接使用实例方法 call_llm, call_tools
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"""
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builder = StateGraph(MessageState)
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builder.add_node("llm_call", self.call_llm)
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builder.add_node("tool_node", self.call_tools)
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builder.add_edge(START, "llm_call")
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builder.add_conditional_edges("llm_call", self.should_continue, ["tool_node", END])
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builder.add_edge("tool_node", "llm_call")
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return builder
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